class Student(object):
    @property
    def age(self):
        return self._age

    @age.setter
    def age(self, value):
        self._age = value

    @age.deleter
    def age(self):
        del self._age

    def __init__(self, name, score):
        self._age = None
        self.name = name
        self.score = score

    def show(self):
        print("my name is :%s, my score is :%d  my age is:%d" % (self.name, self.score, self.age))


def main():
    bart = Student("hello", 21)
    bart.age = 123
    bart.show()


if __name__ == '__main__':
    main()
